The research objectives of this grant are to discover the etiology of hyperoxaluria and recurrent renal calculi in patients with intestinal malabsorption; to establish an effective mode of therapy which will prevent formation of kidney stones in these patients; to determine the mechanisms by which bile salts are sulfated; to investigate the physiological significance of bile salt sulfation in normal individuals, and to determine whether alterations in this process play a role in the pathogenesis of human liver disease.